Paul xarrer



appears.

Patented Dec. 15, 1931 UNITED STATES PATENT OFFIC PAUL KARRER, OF ZURICH, SWITZERLAND,'ASSIGNOR TO HEBERLEIN & (30., A. G OF WA'I'TWIL, SWITZERLAND, A CORPORATION OF SWITZERLAND TREATMENT OF CELL'ULOSE FOR CHANGING ITS ACTIVITY TOWARD DYESTUFFS No Drawing. Application filed. May 1'4, 1929, Serial No. 363,103, and in Germany May 23, 1828..

This invention relates to the treatment of cellulose for changing its activity toward dyestuifs. It is particularly directed to acetylizing cellulose so that it is immunized against substantive dyes. It also relates to a product resulting from such treatment.

In the treatment of cellulose fibres with a mixture of acetic anhydride, glacial acetic acid and a catalyzer such as sulphuric acid, zinc chloride, formic acid, etc., there occurs an acetylization of the cellulose accompanied by a gradual disintegration of the fibre and finally complete solution of the acetylized cellulose in the mixture. By interrupting the process after a certain period it is, of course, possible to obtain partially acetylized fibres which still retain more or less of their original structure. (Cf. British Patent 280,493.) Such fibres show some immunity to substantive coloring matters.

It has been found in accordance with the present invention that the limits between complete solution when the fibre no longer exists and acetylization to a point where the fibres are not destroyed but possess immunityto substantive dyestuffs, lie close together. It is, therefore, extraordinarily easy for toov much acetylizat'ion to occur, and if it does acorresponding weakening of the fibre occurs at the same time. In addition when acetylization continues longer than necessary the immunity of the fibre to the dye lessens or dis- Apparently this is so because acetylization occurs only on the surface of the fibre and the acetylized layer, first formed by further action of the acetylizing mixture is dissolved. v

/ The object of the present invention accordingly istoprovide a simple, inexpensive process of the kind described by which the degree of acetylization of a fibre may be controlled to produce a fibre having immunity to substantive dyestnfi's while substantially preserving the structure and other desirable characteristics of the fibre. Another object of the invention is to provide a product of the kind mentioned having the desired immunity to substantive dyestufis and possessing the strength and other desirable characteristics of the original fibre. Further objects and advantages of the invention will more fully appear in the following description of some preferred methods of carrying out the invention.

I have made the unexpected observation, in accordance with this invention, that trioxymethylene, formaldehyde, polyoxymethylene or other polymers or derivatives of formaldehyde or compounds which liberate formaldehyde under the reaction conditions, designated broadly herein as formaldehyde equalizers, 'when added to an acetylizing mixture of glacial acetic acid, acetic acid anhydride and a catalyzer (for example, sulphuric acid or zinc chloride), act as equalizers of acetylization. They veryextraordinarily and in great measure slow down the weakening or solution of the cotton threads in the acetylizing fluid. By the term equalizer as used above, I mean that the reagent acts to provide a substantially uniform eifect on the surface treated with the acetylizing agent. This effect is a partial acetylization. From my observations the interior of the fiber remains unchanged while the exterior surface is given a skin or coating of acetylized cellulose. For example, cotton which, at

room temperature, is dissolved in an ordinary Examples (1) In a. mixtpre of ten parts glacial acetic acid, eight parts acetic acid anhydride, one part of zinc chloride and two parts of p-formaldehyde, a portion of cotton yarn is immersed at room temperature, about 18 C. and kept there. After two days the treated yarn has a suitable immunity against sub- 1 part of zinc chloride and 4 parts of a so-- lution containing of formaldehyde, a portion of cotton yarn is immersed at room temperature of about 18 C. and kept there. After 2 days the treated yarn is suitably immunized against. substantive dyestufi's which in the course of the next 2 days increases and obtains after 100 to 150 hours a high degree of immunity.

(3) In a mixture of 8 parts of glacial acetic acid, 7 parts of acetic acid anhydride' and 2 parts of zinc chloride, and 1,5 parts of trioxy'methylene, a portion of cotton yarn is immersed at room temperature of about 18 C. and kept there. After 2 days the treated yarn is suitably immunized against substantive dyestufis which in the course of the next 4 days increases and obtainsafter 150 to 17 0 hours a high degree of immunity.

In place of the equalizers mentioned in these examples, other formaldehyde modifications may be employed including polyoxymethylene, other polymers, derivatives of formaldehyde or other combinations which produce formaldehyde in the acetylizing mixture. In place of zinc chloride sulphuric acid may be used as a catalyzer.

Thus while I have described' my improvement in detail and with respect to certain preferred forms, I do not desire to be limited to such details or forms since, as'will be noticed by those skilled in the art. after understanding my invention many changes and modifications maybe made'and the invention embodied in widely different forms without departing from the spirit and scope thereof inits broader aspects, and I desire to cover all modifications, forms and improve ments coming within the scope of any one or more of the appended claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A process of the kind described which comprises treating a substance containing presence of a formaldehyde equalizer and acetylizing'the cellulose-containing substance until it has a partial acetylization sufficient formaldehyde equalizer and acetylizing the fibre until it has a partial surface acetylization suflicient to give it immunity to substantive dyestufi's.

3. A process of the kind described which comprises subjectin cellulose fibre to a bath containing an acety izing agent and a formaldehyde equalizer, and acetylizing said fibre until it has a partial surface acetylization giving it immunity to substantive dyestuffs.

4. A process of the kind described which comprises immersing cellulose in a bath containing glacial acetic acid, acetic acid anhydride, a catalyzer and a formaldehyde e ualizer and acetylizing said cellulose until it has a partial surface acetylization giving it immunity to substantive dyestuffs.

-5. A process of the described which comprises subjecting cellulose fibre to a bath containing glacial acetic acid acetic acid anhydride, a catalyzer and p-formaldehyde and acetylizing said fibre until it has an acetylized surface giving it immunity to substantive dyestuffs.

6. A process of the kind described which cellulose with an acetylizing agent in the v 

